1. Field of the Invention
The invention relates to hydrophobically modified polymers in the form of their aqueous polymer dispersions and water-redispersible polymer powders.
2. Background Art
Aqueous dispersions and water-redispersible powders based on homo- or copolymers of ethylenically unsaturated monomers are known. They are used in the construction sector as binders, where appropriate in combination with hydraulically setting binders such as cement. Examples are found in construction adhesives, plasters and renderings, mortars, and paints. However, they are also used as binders in coating compositions and adhesives and as textile binders, where addition of polymer dispersions or dispersion powders often serves to improve mechanical strength and adhesion. In some application sectors, especially in plasters, renderings, or construction adhesives, demands include reduction of water absorption or water-repellent action, along with improvement in adhesion. To comply with this set of requirements, use is made of hydrophobicized polymer dispersions or hydrophobicized dispersion powders.
WO-A 95/20627 describes hydrophobicized water-redispersible dispersion powders in which the hydrophobicizing additive present comprises organosilicon compounds such as silanes or siloxanes. A disadvantage of silane-hydrophobicized polymer compositions is that these are very effective on silaceous surfaces but do not give adequate hydrophobicization on lime- and carbonate-containing surfaces. WO-A 02/31036 discloses the hydrophobicization of dispersion powders by means of carboxylic esters of polyhydroxy compounds as the alcohol component. EP-A 765898 describes the production of construction materials with low air-pore content by way of dispersion powders which comprise fatty esters.